Skiing on fresh snow, skating on reflective ice or hiking at high altitudes can be harder on your eyes than a day at the beach. Snow, as many East Coast readers may have noticed this week, reflects nearly 80 percent of the sun’s rays. Dry beach sand? Just 15 percent.

Most of us already know that ultraviolet (UV) rays can cause skin cancer and other problems. But that’s not all there is to worry about. “Most people don’t appreciate the damage that UV rays can do to their eyes,” said Dr. Rachel J. Bishop, a clinical ophthalmologist at the National Eye Institute in Bethesda, Md.

Winter or summer, hours of bright sunlight can burn the surface of the eye, causing a temporary and painful condition known as photokeratitis. Over time, unprotected exposure can contribute to cataracts, as well as cancer of the eyelids and the skin around the eyes.

UV exposure also may increase the risk of macular degeneration, the leading cause of blindness in people over age 65. While cataracts can be removed surgically, there is no way to reverse damage to the macula, the area in the center of the retina.

Worried? Consider this article license to buy yourself a new pair of UV-protective shades. But don’t let price and style be your only guides.

“Some cheap sunglasses are great, some expensive ones are not,” said Dr. Lee R. Duffner, an ophthalmologist in Hollywood, Fla., and a clinical correspondent for the American Academy of Ophthalmology.

In fact, some knockoff designer frames may do your eyes more harm than if you’d worn no glasses at all.

Below, some advice on how to find sunglasses that will protect your eyes without plundering your wallet.

READ THE FINE PRINT Prolonged exposure to UV radiation damages the surface tissues of the eye as well as the retina and the lens. Yet while the Food and Drug Administration regulates sunglasses as medical devices, the agency does not stipulate that they must provide any particular level of UV protection. The wares at the average sunglasses store therefore can range from protective to wholly ineffective.

Look for labels and tags indicating that a pair of sunglasses provides at least “98 percent UV protection” or that it “blocks 98 percent of UVA and UVB rays.” If there is no label, or it says something vague like “UV absorbing” or “blocks most UV light,” don’t buy them — the sunglasses may not offer much protection.

For the best defense, look for sunglasses that “block all UV radiation up to 400 nanometers,” which is equivalent to blocking 100 percent of UV rays, advised Dr. Duffner.

CHOOSE THE RIGHT STYLE Ideally, your sunglasses should cover the sides of your eyes to prevent stray light from entering. Wraparound lenses are best, but if that’s not an appealing style, look for close-fitting glasses with wide lenses. Avoid models with small lenses, such as John Lennon-style sunglasses.

Don’t be seduced by dark tints. UV protection is not related to how dark the lens is. Sunglasses tinted green, amber, red and gray may offer the same protection as dark lenses. For the least color distortion, pick gray lenses, said Dr. Duffner.

If you are frequently distracted by glare while driving, boating or skiing, look for polarized lenses, which block the horizontal light waves that create glare. But remember, polarization in itself will not block UV light. Make sure the lenses also offer 98 percent or 100 percent UV protection.

Though the F.D.A. does not require that sunglasses have UV protection, the agency does insist that they meet impact-resistance standards — which basically means they won’t shatter when struck. Even so, if you wear sunglasses while cycling, sailing or gardening, for instance, consider purchasing a pair with polycarbonate lenses, which are 10 times more durable than regular plastic or glass lenses.

AVOID SIDEWALK VENDORS Buy a pair of chic Chanel knockoffs that offer no UV protection, and you might look swell — but your eyes will suffer. The tinted lenses will relax your pupils, letting more damaging radiation hit your retina than if you were wearing no glasses at all.

To play it safe, buy glasses from well-established drug, chain or department stores, rather than from vendors on the street. Shop around: you should be able to find a pair of drugstore sunglasses for $10 to $20 that provide all the protection you need.

Among the recent offerings at Sunglasswarehouse.com, for instance, were wraparound and aviator-style sunglasses that came with full UV protection for just $13.

DON’T FORGET THE CHILDREN Upgrade your children from their Dora and Spider-man toy sunglasses to legitimate shades that offer 98 percent to 100 percent UV protection. Children with light-colored eyes are especially vulnerable to sun damage, said Dr. Duffner. The injury is cumulative, so the earlier children get in the habit of wearing shades, the better off their eyes will be.

If your child plays sports regularly, consider also purchasing sport-specific goggles. Eye injuries are the leading cause of blindness in children, and most of those injuries occur when they are playing basketball, baseball, ice hockey or racket sports.

The National Eye Institute says it believes that protective eyewear could prevent 90 percent of sports-related eye injuries in children.

TEST THOSE OLD GLASSES Reluctant to pop for a new pair of sunglasses? If you already have a favorite pair but don’t know what kind of protection they offer, ask your local eyewear store if they have a UV meter. This device can measure the UV protection of your glasses and help you determine whether you should buy a new pair. “Most opticians have such a meter and can do this very easily,” said Dr. Duffner.

Even if you wear contact lenses that offer UV protection, you’re not in the clear. Contact lenses sit on the cornea in the center of your eyes and so can’t protect the surrounding white area (the conjunctiva) and skin.

“I see many older patients who have growths on the whites of their eyes that were caused by sun damage,” Dr. Bishop said. These yellow bumps, called pinguecula, often lead to eye irritation and dryness and may eventually disrupt vision. To prevent them, adults with contact lenses still must wear sunglasses outdoors.

Lastly, if you wear prescription glasses, you can avoid buying sunglasses by either purchasing clip-ons that attach to your frames or having a UV coating applied to your lenses. Presto, you’ll have two pairs in one.